1. Industrial Field of the Invention
The present invention relates to a connecting structure of a circuit board, an electro-optical device, electronic apparatus provided with the same, and a manufacturing method for an electro-optical device.
2. Description of the Related Art
An electro-optical device such as a liquid crystal display device employs an integrated circuit (IC) device, on which driving IC components are mounted, to connect its driving circuit to a liquid crystal display (LCD) panel. Typical IC devices used for this purpose include a chip-on-film (COF) type wherein a flexible wiring board using a so-called xe2x80x9ctape automated bonding (TAB) package (also known as a tape carrier package (TCP)xe2x80x9d is connected to an LCD panel, and a chip-on-glass (COG) type wherein driving IC components are directly connected to a glass substrate. For instance, the wiring board employing the TCP is advantageous in that it is smaller and thinner than other types of packages, which makes it suited for high-density packaging, and the board is flexible to permit itself to be bent for packaging. These advantages allow the wiring board to find applications in a variety of types of electronic apparatus, including electro-optical devices.
Diverse types of terminals for connection to driving ICs are formed on wiring board employing the TCPs (herein after referred to as xe2x80x9cTCP boardsxe2x80x9d). Hence, to configure electronic apparatus or the like, the terminals of a TCP board are electrically connected to the terminals of another circuit board.
In general, the packaging mode as set forth below is used to connect the terminals of the TCP board and the terminals of another circuit board. With a conductive member such as an anisotropic rubber connector provided between the terminals of the TCP board and the terminals of another circuit board, the TCP board and another circuit board are pressed in a connecting direction thereby to press the terminals of the TCP board and the terminals of another circuit board into contact via the conductive member. This accomplishes electrical connection between the terminals of the TCP board and the terminals of another circuit board.
The connecting structure set forth above, however, has been posing a problem since a flexible wiring board such as the TCP board and another circuit board are pushed against each other to bring them into contact so as to enable the electrical connection. More specifically, in a structure or an environment wherein an adequate force for bringing the flexible wiring board and another circuit board into close contact with each other cannot be secured, if the boards are subjected to external forces, especially vibrations or shocks, electrical connection may not be successfully accomplished, resulting in a continuity failure.
Furthermore, if a rubber connector formed of anisotropic conductive rubber is used for connecting a terminal on an electro-optical device, for example, an LCD panel, to a terminal of a flexible wiring board, then a failure of electrical connection may occur if vibrations, shocks, or other types of external forces are applied.
In addition, a dedicated press-in-contact member such as a case must be used to secure a sufficient contact pressure between a terminal of the flexible wiring board and a terminal of another board, adding to the number of components. Furthermore, to use such a press-in-contact member, the flexible wiring board and another circuit board must be compression-bonded by using a pressing jig. Hence, at locations where direct contact pressure cannot be secured, it is impossible to improve the reliability of contact, leading to a continuity failure.
Accordingly, an object of the present invention is to provide: a circuit board connecting structure which enables contact pressure to be secured without the need for employing a special press-in-contact member so as to achieve higher contact reliability in connecting a circuit board such as a flexible wiring board and another circuit board, which can be configured with less components; an electro-optical device; electronic apparatus provided with the same; and a manufacturing method for an electro-optical device.
To this end, according to one aspect of the present invention, there is provided a circuit board connecting structure for electrically connecting a conductive terminal provided on a first circuit board and a conductive terminal provided on a second circuit board, including:
a conductive member which is disposed between the first circuit board and the second circuit board that oppose each other, and electrically connects the respective conductive terminals;
a structural member disposed on an opposite side from a side where the second circuit board is disposed, in relation to the first circuit board; and
a spacing member disposed between the structural member and the first circuit board.
With this arrangement, the respective conductive terminals are electrically connected by the conductive member installed between the first and second circuit boards. In bringing the conductive member and the respective conductive terminals into contact, the spacing member provided between the structural member and the first circuit board, and the structural member permit adequate contact pressure between the respective conductive terminals and the conductive member.
Thus, the reliable contact with the conductive member achieved by the contact pressure set forth above improves the reliability of the contact between the conductive member and the respective conductive terminals. This ensures successful electrical connection between the conductive terminal of the first circuit board such as the flexible wiring board and the conductive terminal of the second circuit board.
Preferably, in the circuit board connecting structure in accordance with the present invention, the spacing member is provided such that it is associated with at least a part of an area wherein the conductive member is disposed, and a part of the first circuit board is held between the spacing member and the conductive member. With this arrangement, the spacing member is provided such that it is associated with a position where the conductive member is disposed; hence, contact pressure can be applied directly to a position where the conductive member is brought into contact with the respective conductive terminals, leading to further improved contact reliability.
Preferably, in the circuit board connecting structure in accordance with the present invention, the spacing member is formed to be larger than the conductive member in the direction of a surface of the first circuit board. With this arrangement, the spacing member formed to be larger than the conductive member makes it possible to maximize the contact pressure of the second circuit board with respect to the conductive member, permitting higher contact reliability.
Preferably, in the connecting structure of a circuit board in accordance with the present invention, the spacing member is formed of an elastic member. With this arrangement, elastically deforming the elastic member by the structural member allows the contact pressure to be further increased by taking advantage of the elastic force, thus leading to improved contact reliability.
Preferably, in the circuit board connecting structure in accordance with the present invention, the conductive member is formed of an elastic member. With this arrangement, the conductive member elastically deforms in response to a pressure applied to the first and second circuit boards, and the elastic force increases the contact pressure of a contacted portion. The pressing force is generated by the structural member and the spacing member. Hence, the conductive member and the respective conductive terminals can be brought into closer contact, with resultant improved contact reliability.
Preferably, in the circuit board connecting structure in accordance with the present invention, the conductive member has a plurality of rows of conductive portions arranged in a direction in which the conductive terminals are arranged, and insulating portions disposed between the conductive portions. With this arrangement, the conductive member provided with the plural conductive portions formed along the arranged conductive terminals further improves the contact reliability. In this case, the conductive portions need not be in one-to-one correspondence with the conductive terminals.
According to another aspect of the present invention, there is provided an electro-optical device that includes the circuit board connecting structure set forth above. Applying the foregoing circuit board connecting structure to various connecting structures formed in the electro-optical device inhibits continuity failures in connection areas of diverse circuit boards, thereby attaining successful electrical connection in the entire electro-optical device. The connecting structures are useful in achieving lower voltage of the electro-optical device.
An electro-optical device in accordance with the present invention electrically connects a conductive terminal, which is provided on a flexible wiring board electrically connected to an electro-optical display section, and a conductive terminal provided on a circuit board so as to perform display of the electro-optical display section, the electro-optical device including:
a conductive member disposed between the flexible wiring board and the circuit board to electrically connect the respective conductive terminals;
a structural member disposed on an opposite side from a side where the circuit board is disposed, in relation to the flexible wiring board; and
a spacing member disposed between the structural member and the flexible wiring board.
According to the present invention, in a structure wherein a circuit board is provided at the rear side of the electro-optical display section, it is necessary to bend the flexible wiring board for connecting the electro-optical display section and the circuit board. At this time, even if stress or the like caused by such bending remains, good electrical connection between the conductive terminal of the flexible wiring board, the conductive member, and the conductive terminal of the circuit board can be attained by making an arrangement such that the spacing member and the structural member apply pressure to the flexible wiring board so as to utilize contact pressure obtained from the application of pressure. Hence, applying the present invention to a structure, wherein it is difficult to bring a flexible wiring board and another circuit board into close contact with each other, makes it possible to achieve high contact reliability, thus solving a defective continuity problem.
Preferably, in the electro-optical device in accordance with the present invention, the structural member has a support section for supporting the electro-optical display section, and a fixing section connected to the circuit board. With this arrangement, the structural member serves as the support section for supporting the electro-optical display section and also as the fixing section so as to eliminate the need for adding a special dedicated support member or fixing member. This permits a reduced number of parts and accordingly lower cost especially in mass production of electro-optical devices.
The electro-optical device in accordance with the present invention is ideally used for a liquid crystal display (LCD) device. It is preferable in the LCD device that the structural member has a support section on which an LCD panel is rested and a fixing section connected to the circuit board, and that the support section acts also as a light guiding section. With this arrangement, using the light guiding section of the electro-optical display section also as the support section of the structural member obviates the need for adding a special dedicated member. This makes it possible to reduce the number of parts and to reduce cost especially in mass production of LCD devices. Further preferably, the structural member has a fixing section for fixing the LCD panel. This arrangement permits further reduction in the number of parts with resultant further reduction in cost.
The electro-optical device in accordance with the present invention does not limit its application only to an LCD device; it is applicable to a variety of electro-optical devices, including a thin cathode ray tube, a small television employing a liquid crystal shutter or the like, an electro-luminescent display, a plasma display, a CRT display, and a field emission display (FED) panel.
According to still another aspect of the present invention, there is provided electronic apparatus that includes the electro-optical device set forth above. Applying the foregoing electro-optical devices to various structures formed in general electronic apparatus solves the problem of continuity failures in connection areas of diverse circuit boards thereby to permit successful electrical connection in the entire electronic apparatus.
According to a further aspect of the present invention, there is provided a manufacturing method for an electro-optical device wherein a conductive terminal provided on a flexible wiring board electrically connected to an electro-optical display section is electrically connected to a conductive terminal provided on a circuit board, the manufacturing method including the steps of:
disposing a structural member at a rear side of the electro-optical display section, and bending the flexible wiring board toward a rear side of the structural member to oppose the flexible wiring board to the circuit board;
disposing a conductive member in a predetermined area between the conductive terminal of the bent flexible wiring board and the conductive terminal of the circuit board;
disposing a spacing member in a predetermined area between the bent flexible wiring board and the structural member such that the spacing member is positioned to be associated with at least a part of the area wherein the conductive member is disposed; and
defining an interval between the structural member and the circuit board thereby to compression-bond the conductive member to the respective conductive terminals via the spacing member so as to electrically connect the flexible wiring board and the circuit board.
The manufacturing method in accordance with the present invention permits the foregoing electro-optical devices to be efficiently formed.
Preferably, in the manufacturing method, in the step for electrically connecting the flexible wiring board and the circuit board, the structural member has a fixing section connected to the circuit board, and the interval between the structural member and the circuit board is defined by connecting the fixing section to the circuit board. This method allows the conductive member to be easily compression-bonded to the foregoing conductive terminals thereby to permit reliable electrical connection between the flexible wiring board and the circuit board.